1. Field of the Invention
This invention relates to a grinding machine of the type designed to be held by hand for operation.
2. Prior Art
There are known various compact grinding machines which can be held by hand and operated for finishing a welded portion and for removing flashes from a molding. One such conventional grinding machine 10 shown in FIG. 1 is a pot-type one. The grinding machine 10 comprises a cylindrical housing 12 having one end opened, and a high-frequency induction motor 14. The motor 14 includes a cylindrical casing 14a having one end opened and supported within the housing 12, a lid 14b attached to the open end of the casing 14a for closing it, a rotatable shaft 14c extending through the lid 14b and an end wall 14d of the casing 14a and rotatably borne by a pair of bearing members 16 and 18 secured respectively to the end wall 14d and the lid 14b, a rotor 14e fixedly mounted on the shaft 14c for rotation therewith, and a stator 14f mounted within the casing 14a in surrounding relation to the rotor 14e. The shaft 14c extends outwardly of the housing 12, and a flange member 20 of a disc-shape is fixedly mounted on the outer end portion of the shaft 14c. A grinding wheel 22 is mated with the outer face of the flange member 20 in coaxial relation thereto. A retaining member 24 is snugly fitted in central apertures of the grinding wheel 22 and flange member 20, and a bolt 25 is passed through the grinding wheel 22 and the flange member 20 and is threaded into the outer end of the shaft 14c, so that the grinding wheel 22 is clamped between a flange 24a of the retaining member 24 and the flange member 20 and is retained in place. Thus, the flange member 20 serves as a grinding wheel-mounting member. A propeller-type fan 26 for cooling the motor 14 is fixedly mounted on the inner end of the shaft 14c for rotation therewith. An annular passageway 28 is defined by the inner peripheral surface of the housing 12 and the outer peripheral surface of the casing 14a. A plurality of intake apertures 12a are formed through an end wall 12b of the cylindrical housing 12. With this construction, upon rotation of the motor 14, the fan 26 is rotated to feed the air through the intake apertures 12a and the annular passageway 28 and is discharged from an open end 28a of the passageway 28 as indicated by arrows in FIG. 1, so that the lid 14b and the peripheral wall of the casing 14a are cooled by the air so introduced into the housing 12 to thereby prevent an undue heating of the motor 14.
It is desirable that the grinding machine of this type can be as compact and lightweight as possible since it is held by hand and operated to carry out the grinding. The conventional grinding machine 10 has been found not entirely satisfactory, however, in these respects because of the fact that the fan 26 and the flange member 20 for supporting the grinding wheel 22 are mounted separately on the shaft 14c and is spaced along an axis thereof.